Generally, automobiles or vehicles each have an air conditioner for indoor heating or cooling.
In order to improve the convenience of drivers, an automobile air conditioner is being converted into an automation device, and an in-car sensor for automatically measuring the automobile room temperature is essentially included in the air conditioner.
The in-car sensor is installed on the back surface of a grill or an instrument panel of an automobile. The in-car sensor sucks indoor air of the automobile through an aspirator system or a ventilation system, and discharges the sucked air to the outside of the automobile or the inside of the automobile, to thus allow a temperature sensor installed in the air flow to detect the temperature of the automobile indoor air.
Here, the in-car sensor of the aspirator system uses an aspiration motor in which an impeller is integrally formed on a rotor to inhale the automobile indoor air to measure the indoor air temperature of the automobile.
BLDC motors are synchronous motors with fast dynamic response, low rotor inertia and easy speed control.
A brushless direct current (BLDC) motor having a simple structure and good controllability for air conditioning with an air conditioner is used as the aspiration motor, and the structure of the aspiration motor adopts a disk type BLDC motor of an axial gap structure having a gap in the axial direction for thinning.
Meanwhile, the aspiration motor adopts a single-phase motor having a single coil, which is reduced in size and is used in consideration of cost burden. In a single-phase motor, a single stator coil is wound in a coreless/bobbinless type of quadrangular or triangular shape and mounted on a PCB (printed circuit board).
The torque (that is, rotation moment) that rotates the rotor in this single-phase motor is expressed as the product of the force vectors generated in a conductor wire through which current flows in a magnetic field and the distance vectors between the centers of rotation and the points of action of force.
Therefore, in the conventional triangular-shaped stator coil, since the total area of the linear portion of the stator coil (winding) excluding the vertex portion of the stator coil (winding) and the portion where the magnet faces is small when the rotor rotates, there is a problem that the torque for rotating the rotor is small.
In addition, such a single-phase motor is wound with a single stator coil wound in a quadrangular or triangular coreless/bobbinless type and is bonded and used on a PCB with an adhesive. Accordingly, it is difficult to manufacture such a single-phase motor at low cost, and such a single-phase motor may cause poor assembly to occur, and may have a thick film structure.
Korean Patent Registration Publication No. 10-1491051 (Patent Document 1) discloses a structure in which a bobbin is integrally formed in a bearing holder and a coil is wound on the bobbin, in order to improve a process of attaching a coil wound in a coreless/bobbinless type to a PCB (printed circuit board). However, the structure of Patent Document 1 is a thick film structure, the productivity of the coil winding is low, and a separate control PCB is required to have a motor drive circuit.
Meanwhile, in a conventional brushless direct current (BLDC) motor as a single-phase motor, a Hall sensor for detecting the magnetic pole of the rotor and generating a switching signal of the driving current for the stator coil is required. Since the Hall sensor is inexpensive, a driving circuit using only a Hall sensor is used.
In the case that a single Hall sensor is used, the magnetic pole of the Hall sensor is not detected when the Hall sensor is located at the interface of the rotor magnetic pole, and thus the current cannot be supplied to the stator coil. Therefore, there is a dead point at which the self-starting cannot be performed.
In such a single Hall sensor system, as a self-starting scheme, there are a method in which auxiliary magnets are used in the stator so that the Hall sensor deviates from a magnetic pole interface (that is, a neutral point) of a rotor, a method of installing a magnetic material screw on a coil laying portion, and a method of using a specially designed shape of a stator yoke.
In the case of using the above-mentioned Hall sensor, there is a factor of cost increase which requires additional parts to be installed for the self-starting simultaneously with the use of the expensive Hall sensor. Therefore, a method of generating the rotor position detection signal while minimizing the cost increase factor without using the Hall sensor and various sensorless motor drive methods for detecting the rotor position detection signal without using a Hall sensor have been proposed.
Conventionally, in order to connect the stator coils in parallel, it is difficult to wind the two wires simultaneously by binding the start and end portions of the two coils, and thus it is difficult to configure the stator coils in parallel in the single-phase motor.
However, a single-phase motor requiring high drive RPM (rounds per minute) and drive torque requires that the stator coils be connected in parallel while being designed in a productive and efficient manner.